Ventilation Control System and Method

ABSTRACT

An air-conditioning system comprises a fan and a ventilation damper for drawing fresh air into a living space. The damper is able to open and close. The air-conditioning system is adapted and configured to store data indicative of air flow output of the fan over time, and to close the damper based on said data.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to air-conditioning systems and methodsof operating air-conditioning systems. More specifically, the inventionpertains to an air-conditioning system that is configured to adjust theduration and timing of opening and closing a ventilation damper so as tomaximize the efficiency and/or comfort provided by said air-conditioningsystem. Preferably the air-conditioning system can operate in at leasttwo modes of operation that include an energy savings mode and a maximumcomfort mode.

2. General Background

Modern homes and buildings have increasingly been made more weathertight so as to minimize the energy required to condition the air withinsuch structures. However, such improvements have led to the need toforcibly ventilate such structures to avoid the depletion of oxygenand/or buildup of carbon dioxide and other contaminants within theliving spaces of the structures. To this end, the American Society ofHeating, Refrigerating & Air-Conditioning Engineers (ASHRAE) hasestablished standards for the amount of fresh air that should be drawninto a structure to maintain sufficient levels of oxygen and avoidbuildup of carbon dioxide. The standards take into account the volume orfloor space, the quantity of bedrooms, and the number of occupants ofsuch structures. More specifically, ASHRAE 62.2 sets forth the amount offresh air that must be drawn into a residential structure as a functionof how frequently said air is drawn in. Under that standard, if onesixth or more of the required daily fresh air ventilation is broughtinto a structure every four hour period, only a minimum amount of freshair is required to be brought in. Conversely, if the structure isventilated less often than every four hours, more fresh air per day isrequired to be brought in than would otherwise be required. Thus, if astructure is not ventilated continuously, it is advantageous toventilate the structure at least once every four hours. That being said,ventilating a structure has disadvantages. Assuming there is anappreciable temperature differential between indoors and outdoors,ventilating counteracts the air-conditioning, thereby requiringadditional energy to heat or cool. Moreover, ventilating a structurewhen the air-conditioning system is not also heating or cooling air cancause discomfort.

To provide ventilation, it is known to provide a fresh air damper thatis controlled by an air-conditioning system for drawing or forcing freshair directly into the air-conditioning system. It is also known toconfigure such air-conditioning systems to periodically open the damperfor fixed intervals of time in an effort to ensure adequate ventilation.Still further, it is known to operatively connect the damper upstream ofthe air-conditioner's primary blower fan such that the primary blowerfan can be used to draw in the fresh air. In an air-conditioning systemhaving variable speed fan, the blower fan may draw in fresh air atdifferent rates depending upon the operating speed of the fan. Thus,such an air-conditioning system may draw in more fresh air than isneeded.

SUMMARY OF THE INVENTION

An air-conditioning system in accordance with the present inventionpreferably can be operated in at least two modes. One mode seeks tominimize the total amount of fresh air being brought into a structure soas to minimize the amount of energy used to condition (heat or cool)fresh air. Another mode seeks to minimize the time in which theair-conditioning system draws in fresh air while the system is notheating or cooling air so as to minimize periods of discomfort associatewith blowing unconditioned air into living spaces.

One aspect of the invention pertains to a method of operating anair-conditioning system. The air-conditioning system comprises a fan anda ventilation damper for drawing fresh air into a living space. Thedamper is able to open and close. The method comprises storing dataindicative of air flow output of the fan over time. The method furthercomprises closing the damper based on said data.

In another aspect of the invention, an air-conditioning system comprisesa fan and a ventilation damper for drawing fresh air into a livingspace. The damper is able to open and close. The air-conditioning systemis adapted and configured to store data indicative of air flow output ofthe fan over time, and to close the damper based on said data.

Further features and advantages of the present invention, as well as theoperation of the invention, are described in detail below with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a simplified flowchart of the energy savings mode of apreferred embodiment of an air-conditioning system in accordance withthe invention.

FIG. 2 depicts a simplified flowchart of the maximum comfort mode of thepreferred embodiment of an air-conditioning system.

FIG. 3 depicts a schematic representation of the preferred embodiment ofan air-conditioning system.

Reference numerals in the written specification and in the drawingfigures indicate corresponding items.

DETAILED DESCRIPTION

A preferred embodiment of air-conditioning system 10 in accordance withthe invention is shown in FIG. 3. The air-conditioning system comprisesa primary fan/blower 12, a ventilation damper 14, and an electroniccontrol circuit 16. The fan 12 is configured and adapted to draw airfrom within a living space and from the external environment. The fan 12then pushes said air through ducts into the living space. The damper 14is electronically controlled and is configured and adapted toselectively prevent (close) and, alternatively, allow (open) the fan 12to draw in air from the external environment. The electronic controlcircuit 16 is programed to control the operation of the fan 12 and ofthe damper 14. Preferably, the fan 12 is configured to operate atdifferent speeds and the air-conditioning system 10 is preferablyconfigured to alternatively heat, cool, or simply recirculate the airwithin the living space. Like many existing systems, theair-conditioning system 10 of the present invention is preferably amulti-stage system (meaning it can operate at different flow rates basedon demand or personal preferences). Preferably, the electronic controlcircuit 16 is configured and adapted such that some or all of said flowrates can be set by an individual to customize the operation of theair-conditioning system for a particular living space.

As mentioned above, ASHRAE 62.2 sets forth standards for the amount offresh air that should be drawn into a living space per day (hereinreferred to as ventilation). The amount increases if one sixth of theamount is not drawn in each four hour period. The amount is alsodependent upon the size of the living space and the number of occupants.The electronic control circuit 16 of the preferred embodiment isconfigured and adapted such that information indicative of the size ofthe living space (volume or preferably square footage), the number ofbedrooms, the number of occupants (preferably defaults to one person perbedroom plus one extra person), and the percentage of fresh air drawn inas compared to the total fan output when the damper is open can be inputby an installer or other person. The percentage of fresh air drawn in ascompared to the total fan output is preferably measured by the installerusing any of the well-known methods of measuring the same (the fanoutput is specified and therefore only the ventilation air flow rate hasto be measured). Preferably the percentage is measured at maximum bloweroutput or whatever other blower speed draws in the least ventilation airas a percentage. By default, the electronic control circuit 16 isconfigured and adapted to operate the damper 14 and the fan 12 in mannersuch that at least one sixth of the required daily amount of fresh airis drawn in every four hour period. However, in accordance with theASHRAE standards, the electronic control circuit 16 is preferablyadapted and configured to allow someone to set the air-conditioningsystem 10 to ventilate less often. Of course, doing so may be lessefficient since more ventilation air would be required. Still, it couldreduce the number of times the system ventilates when neither heatingnor cooling.

Preferably, the control circuit 16 is configured to allow an occupant tooperate the air-conditioning system 10 in at least two primary modes.For purposes of describing the invention, one such mode shall bereferred to as an “energy savings mode” and another as a “maximumcomfort mode.” A flowchart of the energy savings mode is shown inFIG. 1. The energy savings mode is configured and adapted to draw inonly the minimum amount of fresh air required (so as to minimize theenergy required to condition the air). The energy savings mode isconfigured such that the control circuit 16 opens the damper 14 onceevery four hours to draw in one sixth of the required daily fresh air(herein referred to as the four hour minimum inventory of fresh air). Itis also configured to close the damper 14 after such fresh air has beendrawn in. While the damper 14 is open, the control circuit 16 keepstrack of the fan's 12 operating speed/output (or data indicativethereof) to track how much fresh air is being drawn in based on thepercentage ratio. When the control circuit 16 determines that the“inventory” of fresh air has reached the four hour minimum inventory(the amount required for a four hour period), the control circuit 16closes the damper 14 to prevent additional fresh air from being drawnin. With a rare exception, the damper is preferably maintained closedthereafter during the particular four hour period. It should beappreciated that, while the damper 14 is open, the fan 12 may operate atdifferent speeds based on other temperature settings, user input (e.g.,switching the system to forced recirculation), or demand. Such differentspeeds are controlled by the control circuit 16 in a conventionalmanner. Thus, the duration in which the damper 14 is open may vary froma given four hour period to the next, but in each case the four hourminimum inventory of fresh air would be drawn in. If there is no callfor heating, cooling, or recirculation at any time during ventilation,the control circuit 16 will operate the fan 12 at a “continuousventilation rate,” which is the speed at which the fan would need to runcontinuously for 24 hours with damper 14 open in order to bring in theminimum daily amount of fresh air. Obviously, the continuous ventilationrate is lower than the rate at which the fan 12 operates when theair-conditioning system is heating or cooling. Thus, logically, thecontrol circuit 16 is will open the damper 14 and operate the fan 12continuously during a four hour period in which there has been no callfor heating or cooling (which is a rare event). Assuming the systemfully operational, during such rare events, it should be appreciatedthat the outside and inside air temperatures are close to the same.Hence, the air-conditioning system 10 will continue to ventilate untilthe thermostat calls for heating or cooling, at which point the controlcircuit 16 will operate the fan 12 and damper 14 as initially described.

The maximum comfort mode of operation is configured and adapted to avoidor reduce periods of ventilating when the air-condition system 10 is notalso heating or cooling. In the maximum comfort mode, the controlcircuit 16 is configured and adapted to open the damper 14 each timethere is a call for heating or cooling and to maintain the damper openwhile the air-conditioning system is heating or cooling, unless theinventory (which is tracked by the control circuit 16), reaches aparticular value, which is preferably in excess of a four hourinventory. Preferably that particular value is approximately twice thevalue of a four hour inventory. The control circuit 16 is configured toclose the damper 14 when the heating or cooling terminates. However, ifthe tracked excess inventory reaches or nears zero (a rare event), thecontrol circuit 16 is configured to open the damper 14 and operate thefan 12 at its continuous ventilation rate until there is a call forheating or cooling. Thus, in the maximum comfort mode, the controlcircuit 16 opens the damper 14 when the air-conditioning system 10 isheating or cooling, and only rarely is the damper open whenair-conditioning system is not heating or cooling.

In addition to the forgoing modes of operation, the control circuit 16may also be configured to operate the damper 14 in a more conventionalmanner such as opening and closing the damper 14 on fixed intervals.Thus, it should be appreciated that the air-condition system 10 couldhave additional modes of operation.

In view of the foregoing, it should be appreciated that the inventionhas several advantages over the prior art.

As various modifications could be made in the constructions and methodsherein described and illustrated without departing from the scope of theinvention, it is intended that all matter contained in the foregoingdescription or shown in the accompanying drawings shall be interpretedas illustrative rather than limiting. Thus, the breadth and scope of thepresent invention should not be limited by any of the above-describedexemplary embodiments, but should be defined only in accordance with thefollowing claims appended hereto and their equivalents.

It should also be understood that when introducing elements of thepresent invention in the claims or in the above description of exemplaryembodiments of the invention, the terms “comprising,” “including,” and“having” are intended to be open-ended and mean that there may beadditional elements other than the listed elements. Additionally, theterm “portion” should be construed as meaning some or all of the item orelement that it qualifies. Moreover, use of identifiers such as first,second, and third should not be construed in a manner imposing anyrelative position or time sequence between limitations. Still further,the order in which the steps of any method claim that follows arepresented should not be construed in a manner limiting the order inwhich such steps must be performed, unless such an order is inherent.

What is claimed is:
 1. A method of operating an air-conditioning system,the air-conditioning system comprising a fan and a ventilation damperfor drawing fresh air into a living space, the damper being able to openand close, the method comprising: storing data indicative of air flowoutput of the fan over time; closing the damper based on said data.
 2. Amethod in accordance with claim 1 wherein the fan operates at differentspeeds resulting in different air flow output levels and the data isindicative of a summation of the output levels.
 3. A method inaccordance with claim 2 wherein said data is indicative of a summationof output levels during periods of time while the damper is open ascompared to a duration of time during which the damper is closed.
 4. Amethod in accordance with claim 2 comprising opening the damperperiodically only once every set period of time.
 5. A method inaccordance with claim 4 comprising closing the damper in response to thedata being indicative of achieving a minimum required amount of freshair drawn in through the damper during and for the particular period oftime.
 6. A method in accordance with claim 5 wherein the method furthercomprises operating the fan at the air flow output levels while thedamper is open, and the closing of the damper is indicative of thesummation of said output levels.
 7. A method in accordance with claim 4wherein the damper remains open for different durations over the courseof several of said set periods of time.
 8. A method in accordance withclaim 2 comprising opening the damper based on said data.
 9. A method inaccordance with claim 2 comprising operating the air-conditioning systemin a manner that heats or cools air, and opening the damper in responseto commencing such heating or cooling.
 10. A method in accordance withclaim 9 comprising closing the damper in response to the data.
 11. Amethod in accordance with claim 10 comprising operating the fan duringperiods of time in which the air-conditioning system is not heating orcooling air, and, based on the data, attempting to minimize the periodsof operating the fan during time in which the air-conditioning system isnot heating or cooling and the damper is open.
 12. A method inaccordance with claim 10 comprising opening the damper based on saiddata.
 13. An air-conditioning system comprising a fan and a ventilationdamper for drawing fresh air into a living space, the damper being ableto open and close, the air-conditioning system being adapted andconfigured to store data indicative of air flow output of the fan overtime, and to close the damper based on said data.
 14. Anair-conditioning system in accordance with claim 13 wherein theair-conditioning system is adapted and configured to close the damperbased on the data.
 15. An air-conditioning system in accordance withclaim 13 wherein the fan is configured to operate at different speedsresulting in different air flow output levels and the air-conditioningsystem is adapted and configured such that the data will be indicativeof a summation of a function of said output levels and time intervals.